One of the city’s most well-known interior designers lives in one of its most well-known apartment buildings. Bunny Williams, whose design firm Bunny Williams Inc., was inducted into the Interior Design Hall of Fame in 1996 and was named a “Giant of Design” by House Beautiful in May, lives in a classic six apartment at 1185 Park Avenue.The Gothic style pre-war building and its large courtyard take up an entire Manhattan block.

Ms. Williams wrote a 2005 book, “An Affair With a House” (Stewart, Tabori, and Chang), about her manor house in Falls Village, Conn., where she spends as much time as she can. But though she doesn’t consider the Manhattan apartment her primary residence, Ms. Williams has put careful thought into its design and decoration. “I hope when people come in here they don’t think it was at a certain time,” Ms. Williams, who has owned the apartment for 18 years, said recently. “I really love to mix things.”

Ms. Williams has installed bookcases throughout the home; in the living room they are built into the wall. “I read all the time,” Ms. Williams said.”I’m always looking at my books. My happiest moment is sitting here reading my books at night.” She has transformed the dining room into a partial library, with bookshelves and a round wooden round table that can be used for dinner or as a desk.

On one side of the long, narrow living room, Ms. Williams placed a large, wall size mirror — stained to look antique — that makes the room look wider. She said she designs rooms so that they can evolve, and new furnishings can be added over the years. “I worked on this room a long time,” Ms. Williams said. “It is not so structured so that a lot of things don’t work in here.”

One of Ms. Williams’s favorite pieces in the living room is an early 19th-century French curtain rod. The iron rod, purchased at Malmaison Antiques, a shop on East 74th Street, has a spiderweb design in the middle, with floor-length green curtains hanging down over the room’s one large window. “The cobweb sort of goes along with my love of gardens, and the ironwork is incredible,” she said. She and her husband, John Rosselli, own the garden store Treillages Ltd., on East 75th Street. “I really love all colors, but probably love green the most because it goes with everything,” Ms. Williams said. She found the top of a nearby green table in an antique shop about 38 years ago.

Since Ms. Williams enjoys throwing cocktail parties, she said she wanted the living room to feel comfortable when she is alone or when she has 25 people over. She put another sitting area between the mirror and the fireplace in the middle of the living room, since she said she wants all her guests to be able to have a seat. “I hate not having places to sit down when you have a party,” she said. Her choices include antique Scandinavian chairs that are designed like the ancient Greek klismos chairs (the backs are curved and have no arms), an art deco gray-blue upholstered chair, and an antique Italian armchair with scrolled arms. “To mix a ’50s chair with an 18th-century chair is much more interesting,” Ms. Williams said.”It’s a little bit more intellectual.”

A large wooden 19th-century desk stands in the corner by the entryway to the living room. Ms. Williams included either a desk or table that can be use as a desk in every room of the apartment. “You should put things in a room that makes you go in it,” she said.

For Ms. Williams, that can mean placing personal items alongside the spectacular pieces: Throughout the living room, she has put small rabbit figurines. “When your name is Bunny, you have to have bunny sculptures,” she said.